I'm not sure which version you have downloaded, but I have attempted to address this issue by branching one of the main repositories (kauailabs/nav6) and adding a VI package which can be installed using the VI Package Manager (which you likely already have installed). You can find both the source code vi's and the VI package at
https://github.com/mshafer1/nav6 Go to the release tab and download the vip file. (you can also download the entire zip, but it is likely that the code I was working from is the same as what you currently have.)